The bakery has a window that can be opened.

Talk to the troll. She says she only opens it when it gets hot in the bakery.

Could you make the oven really hot? You need to open the oven, first.

So, while Mr. Fumble is distracting the troll you should insert something that will burn with high intensity in the oven.

Something you were supposed to keep away from fire...

Go get one of those action figures. Burn an action figure in the oven.